Cerotic acid assisted sol-gel synthesis and electrochemical performance of double doped spinels (LiCrxMgyMn2-x-yO4) as cathode materials for lithium rechargeable batteries

Abstract

LiMn2O4 and LiCrxMgyMn2-x-yO4 (x=0.50; y=0.05–0.50) powders are synthesized via sol-gel method for the first time using Cerotic acid as chelating agent. The synthesized spinel samples have been subjected to physical and electrochemical characterization viz., thermo gravimetric analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical characterization viz., electrochemical galvanostatic cycling studies, electrochemical impedance spectroscopy (EIS) and differential capacity curves (dQ/dE). XRD finger print patterns of LiMn2O4 and LiCrxMgyMn2-x-yO4 ratifies the high degree of crystallinity with single phase compound. FESEM image of undoped pristine spinel clearly depicts uniform spherical surface morphology with an average particle size of 0.5μm while LiCr0.5Mg0.05Mn1.45O4 samples depicting the cabbage morphology somewhat large good agglomerated particles of 200nm.TEM images of LiMn2O4 and LiCr0.5Mg0.05Mn1.45O4 particles depict that the synthesized particles are nano-sized (100nm) with spherical morphology and cloudy agglomerated particle size of 200nm. Charge-discharge studies of LiMn2O4 samples calcined at 850°C deliver the high discharge capacity of 130mAhg−1 corresponds to 94% columbic efficiency during the first cycle, while LiCr0.5Mg0.05Mn1.45O4 delivering 123mAhg−1 corresponds to 81% columbic efficiency in the first cycle. Inter alia, all four dopant compositions investigated, LiCr0.5Mg0.05Mn1.45O4 delivers the maximum discharge capacity of 119, 114mAhg−1 in 5th and 10th cycle with a low capacity fade of 0.1, 0.1 mAh g−1cycle−1 and columbic efficiency of 99, 99%.